Magnetometer.



E. GARRETSON.

MAGNETOMETER.

APPLICATION FILED FEB. H. 1914.

Patented June 15, 1915;

WI T/VESSES:

INVENTOR BYZVMQW A TTOR/VEYS,

55 said magnet.

EUGENEGARBETSON, OF BUFFALO, NEW YORK.

MAGNETOHETEB.

Specification of Letters Patent.

Patented June 15-, 1915 "pplicatinn filed February 11, 1914. Serial No. 818,043.

To all whom it may concern:

Be it known that I, EUGENE GARRETSON, a citizen of the United States, residing at Buffalo, in ,the county of Erie and State of New York, have invented new and useful Improvements in Magnetometers, of which thefollowing is a specification.

This invention relates to a device which I have termed a ma etometer and which is intended for regu ating the effect of the magnetic field of a magnet in accordance with some known value which may be de termined by an index on the instrument; also to permit of determining the strength of the magnet; also to enable the magnetic field to be adjusted or varied as to strength for use as a standard of comparison for determining the strength of other magnets or adjusting electric measuring instruments;

2 and also to permit of effecting avariable excitation of a paramagnetic or a diamagnetic body or for other purposes.

It is the object of this invention to provide a device of this character which is very simple and inexpensive in construction, eflicient in operation and not liable to get out of order.

In the accompanying drawings: Figure 1 is a side elevation, partly in section of the idevice embodying my invention, the section being taken in line A-B, Fig. 2. Fig. 2 is an end view of the same.

Similar characters of reference indicate corresponding parts throughout both fignetio material such as iron, one of these pole pieces being preferably secured at its outer end to the front side of the respective end of the magnet while the other pole piece is secured at its outer end to the rear side of 4 the other end of the magnet and the inner ends of the two pole pieces being arranged side by side but spaced apart. The connection between these pole pieces and the magnet may be effected by any suitable means, for instance, by bolts 4, 5, as shown in the drawings. The ends of themagnet are also provided with terminals 6, 7, whereby connection may be made with the parts adapted to be placed in a magnetic circuit with These terminals preferably project rearwardly from the magnet ends and pole pieces and are secured to these parts by the bolts 4, 5.

The inner ends of the pole pieces 2, 3 are provided respectively with openings 8, 9 which are in axial alinement and the space between these ends is preferably filled by a washer or ringlO of non-magnetic material such as brass.

11 represents a tube or casing of nonmagneticmaterial, such as brass, which is arranged with its rear end in the openings of the pole pieces and the washer between the same. The innerend of the front pole piece is preferably thickened and this may be effected in the manner shown in the drawings by placing an extension iron washer or ring 12 around the casing between a rearwardly facing external shoulder 13 thereon andv the front side of the front pole piece 2.

l/Yithin the tubular casing is arranged a shunt member 15 of magnetic material which may be shifted axially in the tube relatively to the pole pieces for the purpose of bridging the same more or less and thus varying the external effect of the magnet in the same measure as the field of the magnet is short circuited. This shunt member is preferably constructed in the form of a circular rod which is provided near its rear end with an external annular groove 14: forming a magnetic gap. Upon moving the shunt member rearwardly so that the wide part 16 in rear of the gap 14 is arranged rearwardly a considerable distance beyond the rear pole piece 3 and the wide part 17 of the shunt member in front of the gap 14 is only arranged Within the front pole piece and washer 12, as shown inFig. 1, no perceptible shunting effect is produced on the magnet and the latter is permitted to exert its full magnetic effort upon any bodies placed in circuit therewith, Upon, however, moving the shnnt member axially forwardly so that its rear wide part 16 thereof is arranged within the rear pole piece and the front Wide part 17 of the same is arranged; within the extension 12 of the front pole piece, then the shunt member bridges the poles of the magnet to its maximum extent and reduces the magnetic output of the magnet at the terminals thereof to. the minimum. By shifting the shunt member so that it bridges the poles of the magnet more or less it .is possible to regulate the external effectobtained from the magnet accordingly to suit different requirements. This adjustment of the shunt member may be produced by various means but those shown in the drawings are suitable and comprise an adjusting spindle 18 arranged in the front part of the tube and carrying the shunt member at its rear end and having a screw connection with the tube so that by turning the spindle the same and the shunt member will be moved forward or backwardly. For this purpose the spindle is provided on its periphery with a screw thread 19 which works in an internal screw thread 20 formed in the bore of the tube. The turning of the spindle and shunt member is preferably eitfected manually by a handle, knob or button 21 arranged on the front end 01? the spindle.

l? or the purpose of determining the position of the shunt member relatively to the magnet poles or for setting this shunt member to a predetermined position relative to the poles this can be readily done by an in dex which preferably comprises an annular row of graduations or scale 22 arranged on the 'front end of the tube and a mark or pointer 28 arranged on the periphery of the spindle and traversing said graduations...

The forward and rearward movement of the spindle and shunt member may be lim ited by any suitable means, those shown in the drawings being satisfactory and con sisting of a stop pin 24- secured transversely to the tube so as to intersect the annular groove or gap 14, whereby the front and rear walls of this groove are caused to engage with this pin at the extremities of the rearward and forward movements of the spindle and shunt member and arrest these parts when the minimum and maximum shunting efi'ect on the magnet is produced. By this means it is possible to establish a standard of comparison for determining the strength of magnets, it is also possible to produce a magnetic field. which may be adjusted or varied in strength for use in connection with electrical measuring instruv merits, and it also permits of efiecting a variable excitation of paramagnetic or diamagnetic bodies.

ll claim as my invention:

1. A device of the character described, comprising a permanent magnet of substantially horseshoe form, pole pieces their outer ends, connected respectively with the opposite poles of said magnet while their inner ends overlap, and a movable shunt member adapted to bridge the inner ends of said pole pieces more or less.

' 2. A. device of character described, comprising a permanent magnet of substanhorseshoe pole pier/es having their outer ends connected respectively with the opposite poles of said magnet while their inner ends are provided with openings which are arranged axially in line, and a shunt member movable through said openings for bridging the pole pieces more or less.

3. A device of the character described, comprising a permanent magnet of substantially horseshoe form, pole pieces having their outer ends connected respectively with the opposite poles of said magnet while their inner ends are provided with openings which are arranged axially in line, a nonmagnetic tube arranged within said openings, and a shunt member of magnetic material movable axially in said tube for bridging said pole pieces more orlessf l. A device of the character described, comprising a permanent magnet of substantially horseshoe form, pole pieces having their outer ends connected respectively with the opposite poles of said magnet while their inner ends are provided with openings which are arranged axially in line, a nonmagnetic tube arranged within said openings, a shunt member of magnetic material movable axially in said tube for bridging said pole pieces more or less, and means for adjusting said shunt member comprising a rotatable spindle carrying said shunt member and having a screw connection with said tube,

5. A device of the character described, comprising a permanent magnet of substantially horseshoe form, pole pieces having their outer ends connected respectively with the opposite poles of said magnet while their inner ends are provided with openings which are arranged axially in line, a nonmagnetic tube arranged within said openings, a shunt member of magnetic material movable axially in said tube for bridging sa'id pole pieces more or less, means for adjusting said shunt member comprising a rotatable spindle carrying said shunt member and having a sore connection with said tube, and means for limiting the axial movement of said shunt member in said tube, comprising two annular shoulders formed by opposite walls of a a circumferential groove in the periphery of said shunt memher, and a pin mounted transversely in said tube in position to be engaged by either of said shoulders,

'tness my hand this 10th day of F bn orlnnnrsouo ruary, 1914b 

